According to the technical requirements to current geological core drilling mud, discussion was made on the mud expert system design method to satisfy the field application. The mud formula derivation model is established on the basis of stratigraphic classification and the engineering examples; formation information database, the formula example database and material information database, etc. are especially constructed for this system. According to the different formations in field drilling constructions, the rapid inquiry of relative engineering cases and application experiences can be realized with the software; the introduction of corresponding mud material, recommend dosage, manufacturers can also be obtained to satisfy the requirement of construction site.